Fire protection sprinkler heads generally include a deflector plate for producing a spray pattern of water (or other fire-retardant liquid). When a fire is sensed, a water stream emerging from the throat of the sprinkler head impinges on the deflector. Often the deflector contains a plurality of fluid deflecting elements (commonly referred to as tines) extending from a central hub, and the tines are relied upon to deflect the water in the desired spray pattern. There are applications, however, in which the deflector includes a surface along which the stream is directed, generally to confine the spray pattern in some way. One such application is the horizontal sidewall sprinkler head, which is generally installed near the top of a wall of a room. Water emerges in a horizontal stream from the throat of such a sprinkler. To aid in distributing the water to the far regions of the room, the upper half of the deflector includes an element that spreads the emerging stream into a fan-shaped spray. Above and extending downstream of this element is a horizontal plate or confining element that further shapes the spray so that it is directed below the ceiling, which may be in some cases within close proximity to the sprinkler head, and towards the far end of the room.